Fuse-testing machine



April 25, 1961 w. A. RHEA 2,981,093

FUSE-TESTING MACHINE Filed July 11, 1956 2 Sheets-Sheet 1 INVENTOR. Wilson A. Rhea H/S ATTORNEYS April 25, 1961 w. A. RHEA 2,981,093

FUSE-TESTING MACHINE Filed July 11, 1956 2 Sheets-Sheet 2 INVENTOR. Wilson A. Rhea A 7' TOR/YE Y5 United States Patent" F FUSE-TESTING MACHINE Wilson A. Rhea, Saltsburg, Pa., assignor to Federal Laboratories, Inc., Saltsburg, Pa., a corporation of Penn sylvania Filed July 11, 1956, Ser. No. 597,199

11 Claims. (CI. 73-35) powder therein which has a selected length and burning rate to afford anywhere from a one second delay time to the more popular periods such as approximately six seconds and up to fifteen seconds delay. The fuses are self-firing, being set burning through action of a spring loaded firing lever which automatically ignites the fuse following removal of a safety pin carried by the fuse, and the time train of powder burns into a grenade detonator at the far end of the train so as to explode the detonator after the proper delay. In customary fashion, the detonator is embedded within a main powder charge which explodes the grenade.

Machines embodying the present invention have a recording clock and other electrical or mechanical instruments in the control apparatus which may be likewise delicately constructed and used to set the fuse burning and start the clock. Before the complete burning time of the time train elapses, the live fuse is bodily transferred, preferably by gravity, to a remote point in the machine at which the resulting explosion will not disturb the adjustment or damage the delicate parts and instruments just named. That remote point is so selected within dropping range of the initial fuse position that the resulting engagement will also subject the burning fuse to the normal 4 ft. impact or drop test while the burning is being completed. The fuse thus lodges in an'explosion chamber appropriately provided at that remote point, and preferably carries the detonator therewith, but without the main powder charge thereabout so as to-minimize the force of theresulting explosion when it materializes.

In the preferred embodiment of the invention, I provide a chamber communicating with that explosion chamber and closed at one end by means of a thin flexible diaphragm. The shock of the detonator explosion rattles this diaphragm at the closed endof the chamberan d the resulting vibratory motion can be readily sensed at the instant it starts bymeans of ya microswitch. or other suitable mechanism responsive to minor movements so as to stop the clock. Elapsed burning time is read directly from the clock. j,

Further features, objects and advantages will eitherbe specifically pointed out or become apparent when .for a better understanding of the invention reference is made to thefollowing written description taken in conjunction with the accompanying drawings inwhich: I I

t Figure 1 is a front elevational view of a machine illus of Figure 1 with certain parts broken away for the sake of clarity, and

Figure 4 is a wiring diagram schematically illustrated in conjunction with Figure 3.

In specific reference to Figures 1 and 2 of the drawings, a test machine illustrating the preferred embodiment of my invention has an I-beam standard 10 secured at the foot by means of a weld 12 to a base plate 14. A- rectangular frame 16 is welded at 18 to the top of the standard 10 so as to be supported in part thereby and isalso welded at 20 to a cylindrical drop tube 22 having a weld 24 at the foot connecting it to the base plate 10. The frame 16 carries a control box 26 having a hand lever 28 to start the mechanism and protruding through one side thereof. At the top the control box 26 supports an electric stop clock 30 and at the opposite side, the box 26 rigidly carries a grenade holder 32. The grenade: holder 32 is spaced approximately 4 ft. above the base' plate 14 and holds a grenade dummy 34 in vertical reg-- istry above the drop tube 22. The grenade dummy 34 has a detonator but no powder charge, and contains a fuse concealed therein and carrying a spring loaded firing lever 36 and a safety pin and pin ring 38.

The drop tube 22 is a thick walled steel cylinder having a loosely fitting explosion door 49 disposed at one side of an explosion chamber 42 in the bottom which the tube 22 defines in cooperation with the base plate 14. Concussion from the explosion dissipates itself both through the open upper end of the drop tube 22 and through the explosion door 40 which loosely fits thereon and gets jolted outwardly. The door 46 carries a reversely bent handle 44. At the opposite side of the explosion chamber 42 from the explosion door 40, the drop tube 22 has a boss 46 connected to support an elbow fitting 48 through a close nipple 50. Another close nipple 52 connects the elbow 48 with the interior of a bell shaped member 53' having a chamber 54 which is closed at its upper end by means of a thin metal diaphragm 56. A cover 58 which is detachably secured to the wide end of the bell shaped member 53 has an opening 60 therein leaving the thin diaphragm 56 unsupported so as to provide a flexible end wall at its center section and a switch actuating finger 62 fomied of a bent metal strip rests on this unsupported center section of the diaphragm. The switch actuating finger is operatively connected to a set of normally closed contacts within a microswitch type pressure switch 64 to open it in response to the concussion pressure of an explosion which passes from the chamber 42 through the elbow 48 and into the chamber 54 thereby rattling the unsupported end v'vall formed by the center section of the diaphragm 56. A set of carrying straps on the microswitch 64 pivot it at one end to a mounting bracket 63 on the cover 58, and the set of carrying straps engage a set of suitably adjustable hold-down nuts 65. A

In Figures 3 and 4 the hand lever 28 passes through a slot 66 within the box 26 to a fixed point of pivotal connection 68 therewithin. The slot 66 limits the length of stroke of the pivoted lever 28 which at the low point of swing engages a normally open push switch 70. At. its outer end the hand lever 28 carries a handle 72 and at a point between the handle and the portion thereof which engages the plunger button of the push switch 70, the hand lever 28 carries 'a' cable anchoring block 74 fast thereto; A flexible cable connector 76 is trained over a sheave 78 mounted in the control box 26 and has one end secured in the cable anchoring block 74 by meansof an adjustable binding screw 80 affording a slack removal adjustment on the cable connector 76. At the other endthe connector 76 is made fast to the mid, portion of a pull block 82 which is rigid at one end with a'lower'shaft 84. At the upper end the pull block 82 has a forked portion which straddles an upper shaft 86. The upper and lower shafts S6 and 84 are slidably mounted parallel to one another and pass through adjacent openings in a set of spaced bearing plates 88 in the box 26 and also through an end plate 90 at the end presenting the grenade holder 32. A helical return spring $2 surrounding each shaft 84, 86 thrusts at one end against the bearing plate 88 at that end and acts in com pression against a stop 94 provided on each shaft so as to urge that shaft to slide to the left as viewed in Figure 3. The helical return spring 92 on the lower shaft 84 normally holds the pull block 82 biased against the adjacent bearing plate 88 and thus acts as return spring for the hand lever 28 to hold it poised in its uppermost position. At the inner end, the upper shaft 86 carries another stop 96 providing an operative lost motion connection with the forked end of the pull block 82. Therefore it follows that when the cable connector 76 is pulled by means of the hand lever 28 the lower shaft 84 moves slightly in advance of the upper shaft 86, but all in the same sequence of motion as soon as the pull block 82 takes up the lost motion with the stop 96.

Atop the control box 26 the electric stop clock 30 can be seen generally to have indicia 98 on the dial which are actually marked off in hundredths of a second in physically constructed embodiments of the machine. A long sweep second hand 100 on the face of the clock reads to these fractional parts of a second, whereas a second accumulator hand 102 reads in terms of total elapsed seconds and both hands cooperate to give an accurately totaled elapsed time reading immediately on inspection. The grenade holder 32 is slightly offset from the end of the box 26 but rigidly afiixed thereto and includes a spaced pair of fixed jaw plates 104. The space between these jaw plates is occupied by the grenade dummy, not actually shown, but its presence is represented in fragments by the firing lever 36 and the safety pin and pin ring 38 normally carried by the fuse therein. The operator retracts the upper shaft 86 to the right by hand as he inserts the dummy between the jaw plates 104 and then .return spring 92 forces the shaft 86 into engagement in the following described manner with the dummy to clamp it against the opposite jaw plate 104. The lowershaft 84 has a hook portion 106 at the outer end over which the operator fits the safety pin ring 38. The upper shaft 86 carries a plunger rod portion 108 of reduced diameter at the end which slides through a'horizontal bore in the holder 32 to a point within the space between the jaw plates 104 where the spring 92 biases it for tightly securing the grenade dummy therein. The reduced plunger rod portion 108 is long enough that it solidly bottoms itself tightly in a retention recess in the side of that grenade dummy and yet leaves the desired lost motion clearance between the pull block 82 and the stop 06 at the opposite end of the upper shaft 86.

The control box 26 holds electrical mechanism including a lamp 110, a main switch 112, a three conductor clock plug 114 connected to the electric clock -30, and an electromagnetic relay switch device 116 which areelectrically interconnected with one another as more particularly shown in Figure 4. p

More specifically in Figure 4, the main switch 112 is included in one of a pair of energized supply conductors 118. The pilot lamp 110 bridges between the two condoctors to indicate when power is on the line. The upper one of the conductors 118 leads to a terminal panel on the clock-30 in a manner hereinafter described to energize it ready for running and a common supply wire '120v leading from that conductor 118 splits into a clock control circuit 122 effective to run the clock and a relay actuating circuit 124 for the electromagnetic relay switch 116. The

the normally open push switch for actuating the clock control circuit and connected through a common ground return wire 130 leading to the appropriate supply conductor 118. The clock control circuit 122 leads through the three-conductor plug 114 to the previously noted terminal panel of the clock 30 and through internal wiring of the clock, eventually leads back through the ground return wire 130 to the proper one of the two supply conductors 118 to complete the circuit. The other supply conductor 118 whichincludes the main switch 112 is connected through the same plug 114 to that terminal panel of the clock 30 so as to energize the same, but without starting the hands.

The first branch 126 of the relay actuating circuit 124 includes the microswitch type pressure switch 64 which is rattled open due to concussion pressure communicated to the closed chamber 54, but is otherwise normally closed. The electromagnetic relay switch 116 has an upper set of contacts a included in the first branch 126 of the relay actuating circuit 124 to form a set of holding contacts which augment the action initiated by the push switch 70 and hold the electromagnetic relay switch 116 in circuit thereafter. The relay switch 116 further includes a lower set of contacts b which are closed thereby to complete the clock control circuit 122 and therefore set the sweep second hand and the second accumulator hand 102 in motion.

In operation of the testing machine of Figures 1 through 4, an operator closes the main switch 112 to energize the clock 30 and prepare it for running operation and at this time the pilot lamp lights. To test the fuse within a grenade dummy 34 which he fits in the machine, the operator swings the hand lever 28 down by sustained pressure on the handle 72 which in the same-motion accomplishes three phases of the starting operation substantially simultaneously. First, the cable connector 76 pulls the block 82 to withdraw the safety pin and pin ring 38 from the fuse and in this instant the lower shaft 84 starts to move simultaneously with initial movement of the handle 72. The pull block 82 takes up the lost motion in its operative connection with the upper shaft 86 and, during the final phases of the swing of the hand lever 28, the plunger rod portion 108 releases the grenade dummy 34 so that it drops from between the fixed jaw plates 104 into the drop tube vertically aligned therewith. Simultaneously with the final phase of swing of the handle 72, the push switch 70 is pressed closed to operate the clock and start the hands 100 and 102. More specifically, operation of the push button switch 70 energizes the electromagnetic relay switch 116 which closes its upper and lower sets of contacts a and b to energize the clock control circuit 122 and also energize the first branch 126 forming the clock holding circuit. The'burning fuse carried within the falling grenade dummy 34 reaches the bottom of the explosion chamber 42 and their fall is abruptly arrested on impact with the base plate 14. The fuse continues burning and the ultimate concussion from the resulting explosion of the detonator carried thereby is communicated to within the closed hell-shaped chamber 54. The pressure of the concussion flexes the diaphragm 56 to temporarily rattle open the microswitch contacts in the pressure switch 64 which preferably are sensitive to only about 0.002" to 0.003" of travel. At this point the pressure switch 64 .open circuits the first branch 126. The holding circuit thus resumes its initial condition ready for another cycle of operation, with the upper and lower relay contacts a and b open and with the normally closed contacts in the t pressure switch 64 closed and with the normally open relay actuating circuit 124 further splits into first and push switch 70 open. The main switch 112 remains closed until the tests are completed, the clock 30 being reset after the elapsed burning time of each fuse is noted.

' .'It will beappreciated that a drop or impact test combined withan automatic elapsed time measurement for burning of the fuse has marked advantages in my test machine. 'The resulting explosion in the chamber 42, remote from the control box 26, is harmless to damage the delicate mechanism therein. At that remote point and by use of a simple microswitch type pressure switch 64, I provide a relatively rugged sensing device not requiring the delicate adjustments and attention to calibration demanded by microphones andsimilarly complicated apparatus previously employed. In comparison with such previous apparatus, I provide a direct reading clock 30 from which elapsed time is readily apparent immediately on first inspection and extremely accurate measurements are possible to the hundredth of a second. The swing action of the hand lever 28 is made with a continuous motion, occurring and being completed practically instantaneously by the operator who then releases the handle 72 and leaves the machine before the fuse can explode the detonator. The machine operation is then automatic to measure and retain the elapsed time reading thereon.

Variations within the spirit and scope of the invention described are equally comprehended by the foregoing description.

I claim:

1. A machine having releasable jaw mechanism effective to tightly hold explodable fuses, starting mechanism operative to set a fuse burning while held in said jaw mechanism, jaw release means having an operative connection to said starting mechanism to release the jaw mechanism substantially simultaneously for the removal and bodily transfer of the fuse to a remote point, means for guiding the fuse while burning, to said remote point,

. by said indicator device in response to each explosion.

2. A machine to measure the burning time of explodable fuses comprising tightly gripping holder mechanism for the fuses, starting mechanism operatively associated with the fuse holder mechanism for initiating burning of a fuse therein, first means including clock mechanism with an electrically driven sweep second hand, second means oper-atively connected to the holder mechanism, saidifirst and second means having actuating means therefor responsive to theoperation of said starting mechanism to {substantially simultaneously :start the sweep hand and release the tight grip of said holder mechanism for removal of said fuse to a remote point for exploding, and means to sense the explosion at said remote point for instantaneously stopping said sweep second hand, said last named means comprising an enclosure aligned with the path of and adapted to take the impact of the fuse so as to capture the fuse in motion while it is still burning, and a vibratible device in connection with said enclosure and connected to the clock mechanism to stop the sweep hand every time an explosion rattles said device, whereby the running time of each fuse captured by the enclosure will be evidenced by a resident reading according to the final point the sweep hand reached when the explosion occurred.

3. A fuse testing machine to measure elapsed burning time in fractions of a second comprising releasable jaw mechanism effective to tightly grip explodable fuses, starting mechanism operative to set a fuse burning While held in said jaw mechanism, first clock mechanism means having a sweep hand, second means having an operative connection to said jaw mechanism to release the fuse for removal and bodily transfer to a remote point, said first and second means having actuating means therefor ree sp'onsive to operation of said starting mechanism to sub stantially simultaneously start the sweep secondhand while concurrently releasing the grip of said jaw mechanism for removal and bodily transfer of a fuse to a remote point, means for guiding the fuse while burning to said remote point, and means at said remote point to sense the resulting explosion for instantly stopping said sweep secondhand, said last named means comprising an enclosure aligned with the path of and adapted to take the impact of the fuse so as to capture the fuse in motion while it is still burning, and a vibratible device in connection with said enclosure and connected to the clock mechanism to stop the sweep hand every time an explosion rattles said device, whereby the running time of each fuse captured by the enclosure will be evidenced by a resident reading according to the final point the sweephand reached when the explosion occurred.

4. A machine to measure elapsed burning time of a fuse simultaneously being subjected to an impact test comprising jaw mechanism effective to hold the fuse while it is ignited, first means in said jaw mechanism releasable to drop the fuse, explosion chamber means to arrest the fall of the fuse having a drop tube registering with the jaw mechanism for the guidance and deposit thereinto of a fallen fuse, second clock means having a sweep hand, said first and second means having separate operating connections to a common actuator for substantially simultaneously dropping the fuse and starting the sweep hand upon ignition of that fuse, an enclosure aligned with the path of drop of and adapted to take the impact of the fuse so as to capture the fuse in motion while still burning, and a vibratible device in communication with said enclosure and connected to the clock mechanism to stop the sweep hand every time an explosion rattles said'device, 'whereby the running time of each fuse captured by the enclosure will be evidenced by a resident reading according to the final point the sweep hand reaches when the explosion occurred.

5. In a machine to measure elapsed burning time of a fuse simultaneously being subjected to an impact test, a frame,*jaw mechanism thereon effective to hold a fuse while it is being ignited, first means included in said jaw mechanism releasable to drop the fuse, explosion chamber means having a drop tube thereabove in vertical alignment with the jaw mechanism to guide the falling burning fuse *thereinto, second clock means having a sweep hand, a hand lever having a swing connection to the frame, said first and second means having separate operative connections to the hand lever for substantially simultaneously dropping the fuse and starting the sweep hand with the same motion of the hand lever, an enclosure aligned with the path of drop of and adapted to take the impact (if the fuse so as to capture the fuse in motion while still burning, and a vibratible device in communication with said enclosure and connected to the clock mechanism to stop the sweep hand every time an explosion rattles said device, whereby the running time of each fuse captured by the enclosure will be evidenced by a resident reading according to the final point the sweep hand reaches when the explosion occurred.

6. In a machine to measure elapsed burning time of a time delay fuse, a frame, jaw mechanism thereon effective to tightly grip a fuse, first means included in said jaw mechanism releasable to drop the fuse therefrom, second means having a sweep hand, third means associated with the jaw mechanism to set the fuse burning, a hand lever swingably connected to the frame, said first, second, and third means having first, second, and third operative connections respectively to said hand lever for substantially simultaneously igniting, dropping, and measuring elapsed burning time of the fuse, said third connection constituting a direct connection to said hand lever, and said first connection comprising a lost motion connection delaying release of the fuse from the tight grip of the jaw mechanism to insure that previous thereto the fuse is set burn- .ing and explosion sensitive means connected to stop the I fuse simultaneously being subjected to an impact test, a

frame, spaced jaw means thereon to tightly hold the fuse in an elevated position, explosion chamber means having a drop tube in vertical alignment below the jaw means to receive the falling burning fuse by gravity thereinto, a handle shiftably mounted on the frame, mechanism having means of attachment at one end to the fuse to start the same and connected at the other end to the handle to initiate starting of the fuse, first means included in said jaw means releasable to drop the fuse therefrom into the drop tube of the explosion chamber means, second means comprising clock mechanism having a sweep hand to record elapsed burning time of the fuse, said first and second means having operative connections to said handle enabling predetermined initial shift thereof prior to starting the sweep hand and dropping the fuse in order that the fuse burning is initiated while the fuse is firmly held in the spaced jaws, and explosion sensitive means in communication with the explosion chamber means and connected to the clock mechanism operable to stop said sweep hand at the final point it reaches as the fuse explosion occurs.

8. Control mechanism for a testing machine adapted to measure elapsed burning time of an explodable fuse simultaneously being subjected thereby to an impact test, said machine having a holder with releasable jaws from which the burning fuse drops toward a remote point, said control mechanism comprising starting mechanism operatively connected with the jaws of said holder for initiating burning of the fuse therein, sweep hand means forming part of an operable clock mechanism including a first switching element sensitive to the operation of said starting mechanism to substantially simultaneously start the sweep hand temporarily, a circuit to augment the first switching element including a second switching element for holding the sweep hand in sustained operation once it is set in motion by the first switching element, and a third switching element included in said circuit and sensitive to the resulting explosion to open the circuit and immediately stop the sweep hand.

9. In a test machine having a holder in which a test fuse is lodged and having operator-shifted means for causing the fuse to be substantially simultaneously ignited and dropped from the holder, the combination of a stop clock to measure elapsed burning time of the fuse and having a control circuit, a control device for actuating said clock control circuit to start and stop the clock, first and second switching elements in circuit with the control device and arranged electrically in parallel with one an- 8 other, said first switching element comprising a push switch in the path of and temporarily actuated by said operator-shifted means for operating the control device to start the clock, said second switching element comprisinga hold circuit element operable to hold the control device in operation for sustaining operation of the clock independently of the first switching element, and a pressure switch element in circuit with said second switching element and responsive to the concussion of the explosion to interrupt the holding circuit and stop said clock.

10. The combination according to claim 9 and including a flexible member forming one wall of a closed chamber and connected to move and operate said pressure switch element under concussion of the explosion, said control device comprising an electromagnetic relayv having multiple contacts, one set of said relay contacts constituting the second switching element aforesaid so as to impart a self-holding action to the relay and another set of relay contacts being included in said clock control circuit for directly controlling the clock.

11. In a test machine having a holder in which a test fuse is lodged and having operator-shifted means for causing the fuse to be substantially simultaneously ignited and dropped from the holder, the combination of an electrical clock having a control circuit, said circuit including therein contacts operated in response to shift of said operator-shifted means and further including therein pressure switch contacts, an enclosure aligned with the path of drop of and adapted to take the impact of the fuse so as to capture the fuse in motion while still burning, and closed chamber means in communication with the enclosure, said chamber means having a flexible member forming one wall of the closed chamber and connected to move and operate said pressure switch contacts under concussion of the explosion set off by the fuse, said control circuit contacts controlling. respectively the starting and the stopping of the electrical clock whereby the clock is operated by said control circuit during the interval between operation of the first named contacts and operation of the pressure switch contacts.

References Cited 'in the file of this patent I UNITED STATES PATENTS Olin et al. "Aug. 15, 1930 1,993,949 Welser Mar. 12, 1935 2,034,658 Jones et al. 2 Mar. 17, 1936 2,294,031 Hobbs et al Aug. 25, 1942 2,370,141 Brunner Feb. 27, 1945 2,660,716 McFarland Nov. 24, 1953 2,777,323 Street Jan. 15, 1957 2,812,655 Curran -2 Nov. 12, 1957 

